A touch panel is an electronic part which is a combination of a display unit like a liquid crystal panel, and a coordinate position input unit like a touchpad, and is a display input device that enables a user to touch an image area, such as an icon, displayed on the liquid crystal panel, and detects information about the position of a part of the image area which has been touched by the user to enable the user to operate target equipment. Therefore, in many cases, a touch panel is incorporated into equipment, such a vehicle-mounted navigation system, which has to mainly meet the need for the user to handle the equipment by following a self-explanatory procedure.
Many proposals for improving the ease of use and user-friendliness of a man-machine device including such a touch panel as mentioned above have been applied for patent. For example, a display input device which, when a user brings his or her finger close to the device, enlarges and displays a key switch which is positioned in the vicinity of the finger so as to facilitate the user's selection operation (for example, refer to patent reference 1), a CRT device which detects a vertical distance of a finger and displays information with a scale of enlargement according to the distance (for example, refer to patent reference 2), an input unit which detects a touch pressure to implement an enlarged display when the touch is a light one and implement a predetermined key operation when the touch is a strong one (for example, refer to patent reference 3), and so on have been known.